A comparison of erythema efficacy of ultraviolet B irradiation from Philips TL12 and TL01 lamps

Abstract

The erythema efficacy of UVB irradiation from Philips TL12 and TL01 lamps has been evaluated and compared. Thirty-seven healthy Thai volunteers were irradiated on the previously unexposed lower back with TL12 and TL01 lamps in doses ranging 100 to 550 mJ/cm2and 360 to 2020 mJ/cm2, respectively. Erythema was evaluated clinically and measured by a narrow- band spectrophotometer before exposure and 24 h after exposure. The threshold doses of UVB that induced barely perceptible erythema (MED(b)) with well- defined border erythema (MED(w)) and the steepness of the dose-response curves for erythema (DRAE) were compared. We found that MED(b) and MED(w) of the TL01 lamps were 4.19 and 4.52 times those of TL12 lamps, which were similar to those calculated from the CIE erythema action spectrum (4.2). However, the DRAE of the two lamps were quite similar. Because the initial dosage of UVB phototherapy is usually given as a percentage of a patient's MED, the initial exposure of TL01-UVB phototherapy should be about 4.2 times that of TL12-UVB.